The present invention relates to steering drive axle devices in general and is particularly directed to a universal joint sealing arrangement for these devices.
Conventional steering drive axles comprise a non-rotatable axle housing and a cooperating wheel mounting spindle. Opposed yokes are associated with the axle housing and spindle with generally vertically aligned trunnions provided to connect the yokes and permit the spindle to swing a limited amount in either direction about the common axis of the trunnions during steering of the vehicle. An enlarged space is provided within the opposed yokes to receive a universal joint which transmits drive between the drive and driven shafts of the axle assembly. The drive shaft extends through the axle housing and the driven shaft extends through the spindle and is connected to the vehicle wheel.
Sealing arrangements are required to protect the universal joint connection used in such devices. The sealing arrangement serves to keep out dirt and moisture and prevent escape of lubricant. Prior arrangements consist of either a single flexible boot or a housing having coacting rigid cover members for enclosing the universal joint. A disadvantage in the former case is that the flexible boot is exposed and therefore susceptable to physical damage and deterioration. A disadvantage in the latter case is that the cover ends are fixed and because of this there is a tendency for the rigid cover members to bind during swinging of the spindle. The bind occurs because the fixed center or pivot points of the opposed cover ends have a tendency to want to move off-center when the cover housing and spindle axes become displaced slightly during pivotal movement about the trunnion axis. Thus, the freedom of movement is restrained to a degree each time the steering operation takes place. This constant occurence of this binding action during steering operations could result in premature failure of the housing and possible damage to the universal joint components. What further complicates matters is that it is a known fact that pivot points in such designs are normally not located directly on-center just because of the normal tolerance build-up that exists when assembling the parts.
While the above sealing arrangements operate in a satisfactory manner when initially installed, each has limitations which make them undesirable after a period of constant operation.